A socket wrench set commonly includes a socket wrench 102 and interchangeable sockets in various sizes. The socket wrench 102 has a drive post 106 or shank, usually of quarter (¼) inch drive, three eighths (⅜) inch drive or half (½) inch drive, onto which a socket 104 fits, as shown in FIGS. 1-3. Sockets are available in metric or English sizes, to fit metric or English hex bolts or nuts respectively. Usually, each socket has a six point receptacle 108 or socket, or a twelve point receptacle or socket (not shown, but widely known and readily understood) at one end of the socket body, and a square receptacle 302 at an opposed end of the socket body 304, although other types of sockets fitting other types of specified fasteners are known. The six point socket, also known as a hex socket, or the twelve point socket is sized to fit the bolt head or nut, and is usually just slightly larger across than the bolt head or nut so as to allow for working clearance. The square receptacle 302 is sized to fit the drive post 106 or shank of the socket wrench 102, and is sized slightly larger across so as to allow for working clearance. Usually, the drive post 106 or shank of the socket wrench 102 and the socket 104 have a ball-detent mechanism (not shown, but readily understood), with the drive post 106 or shank having one, two or four balls that are either spring-loaded and retractable by pressing or retractable with the use of a spring-loaded post 202 extending from the top 204 of the ratchet mechanism 206 on the socket wrench 102. Each socket has a corresponding set of four depressions equally spaced inside of the square receptacle 302, into which the ball or balls of the drive post 106 or shank fit.
In order to insert the drive post 106 or shank of the socket wrench 102 into the square receptacle 302 of the socket 104, the drive post 106 is aligned rotationally and longitudinally with the square receptacle 302 of the socket 104 as shown in FIG. 3, and the socket 104 is pushed onto the socket wrench 102, with the drive post 106 mating with the square receptacle 302. If the socket 104 is not correctly oriented relative to the drive post 106, the socket 104 cannot be pressed onto the drive post 106 and the socket wrench 102, and the user must then manually rotate the socket 104, the socket wrench 102 or the drive post 106 until the socket 104 is aligned with the drive post 106. Such rotation is in a rotation direction 306 about a longitudinal axis 308 of the drive post 106. The socket 104 is removed from the socket wrench 102 by pulling the socket 104 off of the drive post 106, retracting the balls of the drive post 106 either by the pulling action or by pressing the spring-loaded post 202.
Interchangeable sockets are also usable with torque wrenches, nut drivers, breaker bars and impact drivers, although sockets for the latter two generally require specially hardened steel. Socket wrenches and torque wrenches usually have a lever that establishes or reverses direction of a ratchet mechanism, which nut drivers and breaker bars lack. Impact drivers are usually one-way, for loosening stuck nuts or bolts, and can have an electric motor or an impact head that is manually hit with a hammer. Sockets are available in short, medium and extended lengths, and with special inserts for spark plugs. Improvements in the sockets are sought.